(1) Field of the Invention
The present invention relates to non-magnetic single crystal Mn--Zn ferrite which is produced by a solid phase reaction and can be suitably used for sliders in floating type magnetic heads.
(2) Related Art Statement
Magnetic heads have been formerly used in stationary magnetic disc devices (RDD), and a variety of magnetic heads are known. FIG. 6 schematically shows a floating type thin film magnetic head as an example thereof in which a thin film magnetic head is formed on an end face of each of air bearing portions (A surface protective film is removed from the magnetic head in FIG. 6). In FIG. 6, a slider body 2 has a pair of parallel rail-shaped air bearing portions 4, 4 having a given width at a face where the slider body 2 contacts a magnetically recording medium. The thin film magnetic head is provided on that end face of each of the air bearing portions 4 located on a trailing side thereof (on a rear side as viewed in a slide-contacting direction). The thin film magnetic head is constituted by thin film lower and upper magnetic poles and a thin film-shaped coil 8 arranged between front and rear magnetic poles. The upper magnetic pole only is shown in FIG. 1 by a reference numeral 6. Given current is passed through the coil 8 through leads 10, 10. FIG. 7 is a sectional view for illustrating in detail a principle portion of the floating type thin film magnetic head taken along a line VII--VII in FIG. 6. In FIG. 7, a layer 12 of a non-magnetic material 12 (not shown in FIG. 6) is provided on the trailing side of the slider body 2 made of a ferrite, and a lower magnetic pole 6-1 is provided on the non-magnetic material layer 12. An upper magnetic pole 6-2 is provided above the lower magnetic pole 6-1 through an insulating resist 15. The coil 8 is buried in the insulating resist. A magnetic gap 17 is defined between the upper and lower magnetic poles 6-1 and 6-2. A protective film 18 (not shown in FIG. 6) is provided to protect the upper magnetic pole 6-2. The upper face of the slider body 4 is the air bearing portion 2.
When a magnetic material is used as a material for the slider body 2 for the above-mentioned magnetic head, an insulating layer ordinarily needs to be formed between the slider body and the lower magnetic pole. The magnetic poles of the slider for the magnetic head are formed by plating in a magnetic field, and uniaxial magnetic anisotropy needs to be imparted upon the thus formed magnetic film from the standpoint of performance of the head. Therefore, when a substrate having magnetic property is employed for the slider body, it is difficult to impart such a uniaxial magnetic anisotropy upon the slider body. Therefore, non-magnetic Al.sub.2 O.sub.3 --TiC, non-magnetic CaTiO.sub.3 or non-magnetic, polycrystal Zn ferrite is ordinarily used. However, Al.sub.2 O.sub.3 --TiC has poor sliding property between the magnetic disc, and is apt to damage the magnetic disc. On the other hand, since CaTiO.sub.3 has a large coefficient of friction relative to the magnetic disc, the slider body is apt to damage the magnetic disc through contact with the disc and in turn the slider itself is likely to be damaged. Further, when a special shape such as a bridging structure in a negative pressure type slider or a shape trail structure is employed as a pair of the bearing portions 4, 4 of the slider body 2, such structures must be usually realized by an ion etching process. Consequently, a producing apparatus is costy. Furthermore, since the etching speed is low, it exerts a large influence upon the cost of production.
In order to solve the above-mentioned problems, Japanese patent application Laid-open No. 3-126,662 discloses an example in which a non-magnetic, polycrystal Mn--Zn ferrite is used as a slider for a magnetic head. However, as mentioned above, if air bearing portions are employed, mechanical working steps become troublesome, and take a long time period. Further, orientations of crystals are not uniform in this MN--Zn ferrite. Therefore, when the air bearing portions are formed by chemically etching the non-magnetic, polycrystal Mn--Zn ferrite, the etching speed differs depending upon crystal grains and accordingly workability of the ferrite in a straight shape becomes deteriorated. As a result, adverse effects appear upon the dimensional stability and the floating performance of the magnetic head.
Furthermore, Japanese patent application Laid-open No. 4-53,013 discloses an example in which a non-magnetic, single crystal ferrite obtained by a so-called Bridgemann process for the production of the single crystal ferrite from a melt is used as a substrate for a magnetic head in a VTR. However, segregation of the composition cannot be avoided in this process. Therefore, when air bearing portions are formed by chemical etching, the etching speed varies. Consequently, good dimensional stability is difficult to realize, and this process cannot be employed for industrial production. Further, if a non-mangentic, single crystal Zn ferrite containing TiO.sub.2 is used as a slider for an RDD, a chemically etching speed is small compared with the case of the single crystal Mn--Zn ferrite. Consequently, it is extremely difficult to form air bearing portions from this Zn ferrite, with the result that the slider body of such a single crystal Zn ferrite cannot be produced.